The candidate for the proposed quantitative career development award has multidisciplinary training and research experience in physics and the computer sciences as well as in neurophysiology and functional brain imaging. The overarching goal of the current proposal is to enhance the candidate's expertise in developmental cognitive neuroscience. Through a multidisciplinary program combining education, mentoring, and the completion of an innovative research study, the candidate seeks to investigate brain function in both typically developing children and children with specific neurodevelopmental disorders. As a result, the proposed program will not only improve the candidate's research skills and expertise, but will also contribute to the discovery of essential knowledge about the normal cognitive development and its disruption. The institutional resources, environment, and opportunities for research and collaboration in functional neuroimaging of children and adults at Stanford University are exemplary. At the end of the award, the candidate expects to: (1) possess the skills needed to be an independent investigator in developmental cognitive neuroscience; (2) to have received funding as an independent investigator; and (3) to become a leader in the scientific study of basic and clinical developmental cognitive and systems neuroscience. As part of this award the candidate will complete a mentored research project titled "Longitudinal fMRI study of cognition in children" under the mentorship of Dr. Allan Reiss at Stanford University. In this proposal, the candidate plans to use fMRI to investigate the typical and atypical patterns of development of cognitive functions in children during a critical stage in the development of higher cognitive function. Twentyfive typically developing children and twentyfive children with Fragile X, a neurodevelopmental disorder, who are 68 yrs old (mean age 7 yrs) at the start of the study will be imaged twice, two years apart. Brain images will be acquired while children perform working memory and arithmetic reasoning tasks. Behavioral performance measures will be acquired simultaneously to determine how well and how efficiently individual children perform these tasks. Standardized neuropsychological. assessment will be performed on each individual to determine the overall level of cognitive ability in each child. The relation between changes in the level and extent of brain activation, task performance and overall IQ will be analyzed to determine domain specific and domain nonspecific features underlying the neurobiology of cognitive development. The proposed fMRI research project will yield important new and more precise information about the neural bases of the development of higher cognitive processes in children as well as its disruption in atypical development.